The purpose of this report was to describe the clinical, radiological, and histopathological features of a case of regional odonto- dysplasia (RA) in a seven-year-old boy who was followed for approximately two years. The case is unusual in that the dysplasia occurred in the mandible, and there was a normal-appearing tooth within the lesion, suggesting that there may be local factors that determine susceptibility of individual teeth in RA. The diagnosis of RA was based on the typical features of "ghost" teeth and evidence of disrupted calcification characterized by psammomatous bodies, hypomineralization of enamel, and the presence of interglobular dentin. Sequential orthopantomograms provide evidence of delayed dental development.